Transport across cell membranes Flashcards
Simple vs Facilitated Diffusion?
Simple = molecules move directly through the phospholipid bilayer
Facilitated = molecules pass through transport proteins (large use carrier, charged use channel)
Factors that affect rate of diffusion?
surface area (increase = increase rate of diffusion)
concentration gradient (increase = increase rate of diffusion)
thickness (decrease = decrease diffusion distance = increase rate of diffusion)
temperature (increase = increase kinetic energy = molecules move faster = increase rate of diffusion)
size of molecules (smaller molecules = increase rate of diffusion)
What is Ficks Law?
(Surface Area x Concentration Gradient)/Thickness
Define Osmosis?
movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane
Which liquid has the highest water potential?
distilled/pure water
has a value of 0kPa
lower water potential by adding solutes (makes water potential negative)
water moves from less negative water potential (e.g. -35 kPa) to more negative water potential (e.g. -75 kPa)
Surround animal cell with pure water?
swells and burst (water enters by osmosis)
Surround plant cell with pure water?
swells but does not burst
cell wall prevents it from bursting
made of cellulose – strong material
the cell is Turgid
Surround animal cell with concentrated sugar/salt solution?
shrinks (water leaves by osmosis)
Surround plant cell with concentrated sugar/salt solution?
water leaves by osmosis
cell wall prevents cell from shrinking, keeps it rigid
the protoplast (cell membrane plus contents) shrink
the cell is Plasmolysed
Define Active Transport?
movement of molecules from an area of low concentration to an area of high concentration using ATP and carrier proteins (against concentration gradient)
Describe the process of active transport?
molecules (in area of low concentration) bind to carrier protein
ATP breaksdown to ADP, Pi and Energy
the Pi and Energy cause the carrier protein to change shape
carrier protein releases molecules on opposite side (in area of high concentration)
the carrier protein releases the attached Pi to return to its original shape
Absorption of Glucose and Amino Acids in SI via cotransport?
sodium ions are actively transported from the cells lining the SI into the blood
lowers the sodium ion concentration in the cell
therefore sodium ions move from the lumen of the SI into the cell
this pulls in glucose and amino acids via a cotransport protein
therefore glucose and amino acids builds up in the cell and moves into the blood by diffusion
